Zinc base alloy



Feb. 8, 1966 Filed April 30, 1963 Z INC BASE ALLOY 2 Sheets-Sheet 2ftlbs. P,S.I. 40

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Z LEAD Z LEAD FZ G. 9 Mbs. ETG. PISA. 40 43000 V1 l I A c D A B c DDESIGNATED ALLOYS DESIGNATED ALLOYS INVENTOR ATTORNEYJ United StatesPatent O 3,234,016 ZINC BASE ALLOY Leslie J. Larrieu, San Marino,Calif., assignor to Morris P. Kirk & Son, Inc., Los Angeles, Calif., acorporation of Nevada Filed Apr. 30, 1963, Ser. No. 285,169 4 Claims.(Cl. 75-178) This is a continuation-in-part of copending applicationS.N. 211,376 iiled July 20, 1962 and now abandoned, which, in turn, is acontinuation-in-part of application S.N. 68,674, filed November 14,1960, now Patent No. 3,083,096, granted March 26, 1963.

This invention relates to a high purity alloy of zinc base with improvedmechanical and physical properties containing aluminum and copper asmajor alloy constituents'and beryllium and/or magnesium as a minor alloyconstitutent present in small but highly critical amounts that areextremely determinative of the improved properties.

The most important mechanical properties that are essential for the bestperformance of a forming die are, tensile strength and impact strength.Brinel hardness also is important, as are the physical properties ofgrain refinement, dimensional stability upon ageing and castability.Adequate tensile strength insures commensurate adequacy of compressivestrength because of the mutual proportional relations of these twostrength properties.

Since the introduction of the basic 4% aluminum, 3% copper, .05%magnesium, balance zinc, sand casting alloy, in 1939, there has exi-sted.a need to improve the impact strength and tensile strength of thisalloy. Today this need is even more urgent because of the expandingtechnologies of the aero-space industries, which pose even more exactingand more severe mental forming tasks. Research work directed toward suchalloy improvement resulted in the alloy disclosed in Patent No.2,940,846, granted to me on lune 14, 1960. The patent discloses that aradical reduction in the nominal .05% magnesium content of the prior artalloy to an amount less than .03%, and `preferably less than .02%,rennes grain size, increases tensile strength and impact strength andgenerally improves the basic 4% aluminum, 3% copper, balance zinc,lalloy in all mechanical and physical properties.

Additional research directed toward the improvement of this basic alloytype has resulted in the discovery that the addition of small, buthighly critical amounts of beryllium to an alloy containing 4% aluminum,3.25% copper, .01% magnesium, balance zinc, very substantially increasesthe tensile strength and impact strength of the alloy. Otherimprovements include a slight increase in Brinell hardness, a mostsubstantial improvement in castability and a marked additionalrefinement of grain size. This discovery was unexpected in that itrepre- Vsents complete departure from previous attempts to relne grain,`and obtain additional mechanical and physical property improvements, bythe addition of potentially helpful agents, including the addition ofberyllium in amounts approximating .05 The .05% beryllium addition, aswill be revealed hereinbelow, detracts rather than helps in the.attainment of the desired improvements.

The use of beryllium as a minor alloy constituent in alloys of zinc baseis known. Patent No. 3,037,859 granted to me on June 5, 1962, disclosesthe use of .05 to .110%

`beryllium in an alloy of zinc base containing substantial amounts ofcopper, such Vas 8%, lesser amounts of aluminum, such as 3%, and minoramounts of magnesium, such as .05%. This alloy possesses a very goodtensile strength, compressive strength and Brinell hardnes and retainsthese properties in substantial amounts when sub- 3,234,016 PatentedFeb. 8, 1966 ICC jected to operating temperatures up to 400 F. Theimpact strength of the alloy is about equivalent to that possessed bythe 4% aluminum, 3% copper, .05% inagnesium, balance zinc alloy, orabout 8 ft. lbs. Melting and casting temperatures are somewhat in excessof those required for the alloys containing 3% copper.

Accordingly, it is an important object of this invention to provide azinc base alloy which, upon being sand cast, possesses maximizedmechanical and physical properties.

Another object of this invention is to provide an improved zinc basealloy which readily can be melted in conventional melting equipment andwhich readily can be cast in sand, permanent molds and pressure diecasting methods for producing sound forming dies, heavy duty toolingplate, exceptionally strong die castings having maximum high tensilestrength, impact strength, and dimensionai stability.

Additional objects and advantages of the invention will become apparentfrom the following description.

Briefly stated, in general terms, the objects of this invention areattained by providing a zince base alloy of high purity containing fromabout 3.5% to about 4.5% aluminum, from about .5% to about 3.5% copper,from a trace to about .03% magnesium, from about .0002% to about .02%beryllium, and the remainder zinc. A preferred alloy contains from about3.8% to about 4.2% aluminum, from about 1.5% to about 3.25% copper, from-about .005% to about .025% magnesium, from about .005% to about .012%beryllium and the remainder zinc. An especially preferred alloy containsabout 4% aluminum, about 3.25% copper, about .01% magnesium, about .01%beryllium, and the balance zinc.

All of the above metals are substantially pure that is the aluminum,copper, magnesium, beryllium, and zinc are all substantially pure.However, some impurities do creep into the processing of the metals butthese are kept to a very low maximum. In fact the soft metalcontaminants consisting of lead, tin, cadmium, bismuth, and antimony areheld to a collective maximum of .0066% with lead being held to a maximumof .004%. Iron is held to a maximum of .02% while silicon is held to a.003% maximum content. Other contaminants such as manganese, chromiumand titanium are held to a collective maximum amount of .005%.

Applicant has used a commercial and ravailable special high grade zincin which the Zinc content is 99.99796% pure. Included in the impuritiesis lead at .0008%, iron at .0005% and cadmium at .00004%. It doescontain .0007% copper which is not considered an impurity because copperis used in this alloy. Applicant has used a commercial and availablespecially high grade aluminum which contains 99.85% aluminum with .07%silicon and .07% iron and .01% other metals. The copper used byapplicant in the manufacture of the present alloy as set forth in theapplication, has been assayed to include .005 tin, .003% lead, leaving acopper content of 99.992% pure.

The beryllium copper master alloy used by applicant has been found tocontain .005% lead, .005% tin, .06% silicon, .005% chromium, .01%nickel, .06% iron and .01% cobalt. This is the 4% beryllium coppermaster alloy which is used by applicant. However, as Will be explainedlater, applicant takes this beryllium copper master alloy and makesanother master alloy with the same before putting this into the otherconstituents metals of the alloy. This beryllium copper alloy alsocontains some zinc, some aluminum and the balance copper.

A more detailed description of my invention is given below withreference to the attached drawings', wherein:

FIG. 1 is a graph showing the effect of copper on the 3 tensile strengtho fa sand cast zinc base alloy containing 4% aluminum, .008% magnesium,and .01% beryllium solid line, and of the same alloy with berylliumbroken line;

IFIG. 2 is a similiar graph showing the effect of copper on the impactstrength of a sand cast zinc base alloy containing 4% aluminum, .008%magnesium, and .01% beryllium 'solid line, and of the same alloy with 0%berylliurn broken line;

FIG. 3'is .a graph 'showing the effect of magnesium on 'the ltensilestrength of a sand cast Zinc base alloy containing4%"alur`ni'num, 3%copper, and .005% beryllium solid line, and of the same alloy With 0%beryllium broken line; 4 4 I a FIG. `4 is a similar graph showing theelect of magnesium 'on lthe impact strength 'of a sand cast zinc basealloy `containing 4% aluminum, 3% copper, andl.005% beryllium solidline, and of the same alloy with 0% beryllium broken line; a a

FIG. 5 'is a graph lshowing the etect y'of lberyllium on the tensilestrength of a sand kcast zinc base alloy containinglft4% aluminum, 3.25%copper, .and .01% magnesium;

F1G. j6 is a similar `'graph showing the effect of beryllium on theimpact 'strength Vof a sand cast zinc base alloy con-` taining 4%aluminum, 3.25% copper, and .0 l'ma gnesium;

FIG. 7 is Va graph showing the etect of lead on ythe tensile strength ofl.a sand cast Zinc base alloy containing '4% aluminum, 3.25% copper,.'01%"`mag`nesium, .01% beryllium;

FIG, 8 i's a similar graphshowingthe eect of lead on the impact strengthof a sand cast zinc base alloy containing the same alloy as described inconnection with FIG. 7;

FIG. 9 is a bar graph showing the comparative ,tensile strengths ofthree 'sand cast zinc base alloys:

(a) Which contains 4%` aluminum, 3% copper and .05% magnesium;

a -(b) Containing 4% aluminum, 3.25% copper and ;005% magnesium; v

(c) Containing 3% aluminum, 8% copper and .05% magnesium 'and .05beryllium;

(d) The alloy of this application, which contains 4% aluminum, 3.25%copper, .01% magnesium, and 0l% beryllium;

FIG. `1`0`is a similar bar graphshowing `the comparative impactstrengthsof the four alloys (a), (b),"(c), and (d), defined abovein'describing FIG. 9; Y l

(The basic'rnechanical vproperty, relationships and effects of thealloying elements comprising the alloy of this invention Will be betterundenstood after consulting ythe graphs presented in FIGS. 1 through l0.y

presents the eiect of the addition of copper Y'v1/ith '.01% beryllium inthe solid line of the graph,-and copper 'Without beryllium, in thebroken line, `uponthe lsand cast tensile strength of they '4% aluminum,.008% magnesium, balance zinc, alloy. It is readily evident thatincreased 'copper content t produces increz'ised, tensile strength, andthat the inclusion of .01% beryllium results in a gain of approximately4000 p.s`.i. tensilefstrengthffor each copper percentage from A1.5% to4.5%.

F'GZ presents 'the eliect of the additionofcoppe'r with .01% beryllium,in the solid line of the graph, and

copper Without beryllium, in the :broken line, upon sand cast impactstrength of the 4%, aluminum, .008% magriesim, balance zinc, alloyofFIG. l. This relationship:

is one of inverse proportionality in which the eect of beryllium isindicated to be one of retention of higher increments of impact strengthfor 'all levels of copper content from .5% to 4.5%.

Table 1l given ibelow contains the test data used to plot the brokenlines ofthe graphs of FIGS. l and 2;

' Table 1 iect yof ycopper on the tensile strength, impact strength 'andBrinell hardnessv 'number of a sand cast zinc base 4 Y Y alloycontaining 4% aluminum, .008% magnesium, and balance zinc.

Percent Tensile Impact Brinell Cu strength strength hardness added(psi.) (it. lbs.) (number) 5 29, 800 30.0 85. 7 1. 0 32, 600 30. 5 92.6 1. 5 33, 300 31. 5 9216 2. O 35, '000 r32. 0 l 96. 3 2. 5 35, 900 33.0100 3.0 36,900 31. 0 100 3. 25 37, 200 30. 0 104 3. 5 37, 500 27. 5 1044. 0 38, 800 17. 5 109 4. 5 40, 000 14. 2 109 Table ,2

Effect of copper on `the tensile strengtlnr impact strength and Brinellhardness number, of a `sand cast Substantialimprovement` inmelting/characteristics and castability as well as marked refinement ofgrain size'are obtained by the addition of small 'but critical 4amounts`of beryllium yalone to the alloy of this invention. Beryl'- liumaddition alone` in critical amounts tothe alloy, also improves `tensile`strength and `impact strength.` However, maximum improvement'isobtained ffrom the addition of two elements namely, berylliumfandmagnesium in the critical amounts or ranges specied. Theseaddil tions ofsmall but critical amounts of beryllium'and-mag-z t Vnesiulnbeneit thealloy with regard `to tensile strength and impact strength insubstantial mannenfor all increr Y ments of copper over the range :fromabout :5% to about 4.5% as caribe seen by 4examining FIGS. `1 and E2`and Table 2.

However, the copper-contentfof the: alloyas set forth in FIGS. l and 2must be limited to .amaximum of'3.`5%. This limitation on vnriaXinuLrncopper, must be observed in order topreventa substantial loss of impactstrength. Attention is directed-to the graph of FIGJZ 'showing aconsiderable and fast drop olf of thewimpact strength when the coppercontent vis :over 3.5%, both with and 'Without beryllium. It has beenconiirmed ,by multiple tests ythat a copper amount of 3.25%,l which :isAWithin the preferred range previously stated, gives the bestcornbination of mechanical gproperties fWhen both impact. i

strength Eand tensile strength are considered.

FIG. 3 presents the eiect of the addition tofmagnesium with .005%beryllium, in `the vsolid *line of the graph,

and magnesium Without beryllium,- infthe'brokengline,

upon the sand cast tensile strength of the .4% aluminum, 3% copper,balance zinc, alloy .f A :critical `irange kforv magnesium `both withand without` the '.005% vberyllium addition is indicated. The optimum'ris indicated to Ybe v about .01% to about 025% magnesum. It is Vnote;worthy that the .005% beryllium addition accounts foi' f an increase `ofoverl3,000 p.s.i; tensile lstrength'for Yall levels ofmagnesiumcontentsthrough vIthe range from .01% to .04%.

FIG. "4 presents the effect of the'addfitionfof magnesiumv -with .005%beryllium, Vin the solid r.li'nef of thelgraph,.and

magnesium without beryllium, in the broken line, upon the sand castimpact strength of the 4% aluminum, 3% copper, balance zinc, alloy ofFIG. 3. A critical range for magnesium is presented with an evidentimprovement from the beryllium addition over the range of from about"%magnesium to about .03% magnesium. The optimum from the magnesiumaddition resides within the range from about .005 to about .025% forboth the magnesium alone and the magnesium with beryllium.

Table 3 given below contains the test data used to plot the broken linesof the graphs of FIG. 3 and 4:

Table 3 Effect of magnesium on the' tensile strength and impact strengthof a sand cast zinc base alloy containing 4% aluminum, 3% copper andbalance zinc.

Percent Mg Tensile Impact added strength strength (p.s.i.) (it. lbs.)

Zero 35, 000 2l. 0 005 36, 000 30.0 010 36, 700 31.8 015 37,000 32.0 02037, 300 32. 0 025 3G, 600 30. 0 030 35, 400 28. 0 040 33, 600 22. 0

Table 4 given below contains the test data used to plot the solid linesof the graphs of FIGS. 3 and 4:

Table 4 Eect of magnesium on the tensile strength and impact strength ofa sand cast zinc base alloy containing 4% aluminum, 3% copper, .055%beryllium and balance zinc.

- Percent Mg Tensile Impact added strength strength (p.s.i.) (it. lbs.)

Zero 36, 000 26. 5

It has been discovered that the presence of small amounts of magnesiumin the zinc base alloy containing beryllium is not necessary to achievethe results. The small amounts of magnesium however, do improve theimpact strength and the tensile strength over that of a berylliumcontaining alloy without the magnesium addition. The presence ofberyllium in the alloy does enhance the d imensional stability thereof,produces reined grain, improves the castability and also improves theimpact strength and the tensile strength. This is clearly shown in thegraphs of FIGS. 3 and 4. The percentage of magnesium added, withberyllium of course, as shown by the solid line of the two graphs, doesincrease the impact and tensile strengths. However, it is to be notedfrom an examination of both FIG. 3 and FIG. 4 that a substantialimprovement for tensile strength and a very substantial improvement forimpact strength are obtained for the alloy containing 4% aluminum, 3%copper, .005% beryllium and essentially no magnesium over that obtainedfor the same magnesium free alloy without beryllium. Specifically theimprovements are 1000 p.s.i. tensil strength and 5.5 ft. lbs. impactstrength.

Thepresence of magnesium in relatively low amounts and speciiically inthe preferred range of .005 to .025%

yproduces maximum mechanical properties for the alloy containing 4%aluminum, 3% copper, .005% beryllium,

6 balance Zinc of high purity both in the cast condition and after aging1 year at room temperature.

In the absence of magnesium this same composition yields somewhat lowermechanical properties in the as cast condition, however, theseproperties improve upon aging and substantially exceed those obtainablefrom the same alloy composition without beryllium, but containingmagnesium over the range .01% to .05% and higher, after aging l year atroom temperature.

This property of beryllium that improves the magnesium free alloys inmechanical properties after aging at room temperature has been found tobe maximum in amount for the desired alloy of 4% aluminum, 3.25% copper,.01% beryllium balance zinc and with the soft metal impurities presentin a collective amount of less than .0066%.

FIG. 5 presents the eifect of the addition of beryllium, over the rangeof 0% to .04%, upon the sand cast tensile strength of the 4% aluminum,3.25 copper, .01% magnesium, balance zinc, alloy. The critical amount ofberyllium for maximum tensile strength is from about .008% to about.012%. It is to be noted that the .04% beryllium alloy has a tensilestrength which is substantially equivalent to that possessed by thealloy without the beryllium addition inasmuch as both .0% and .04% areapproximately at the 37,000 lb. level. It has been found from multipletest evaluation that additions of beryllium in excess of .04% to thisalloy reduces both the tensile strength and the impact strength of theresulting alloy below that possessed by the beryllium free alloy.

FIG. 6 presents the effect of the addition of beryllium upon the sandcast impact strength of the 4% aluminum, 3.25% copper, .01% magnesium,balance zinc alloy of FIG. 5, over the range of 0% to .04% beryllium. Itis evident that a high degree of criticality of the amount of addedberyllium also applies to the property of impact strength. Beryllium inthe amount of about .02% is the indicated absolute maximum addition. Thedesired optimum amount is indicated to be from about .008% to about.012% beryllium.

Although in the broad range the lower limit of beryllium has been placedat .0002% and that this amount has been found to have beneficial resultsas shown by the graphs of FIGS. 5 and 6, it has been found that thelower limit of beryllium may be placed at .0005%. With this increasedamount of properties of the alloy are likewise increased as shown by thegraphs.

Table 5 given below contains the test data used to plot the graphs ofFIGS. 5 and 6:

Table 5 Effect of beryllium on the tensile strength and impact strengthof a sand cast zinc base alloy containing 4% aluminum, 3.25 copper, .01%magnesium, and balance z1nc.

Percent Be Tensile Impact added strength strength (psi.) (ft. lbs.)

zero 27, 000 32. 0 005 29, 800 36. 0 008 41, 000 37. 8 010 41, 000 38. 0015 40, 600 37. 0 020 39, 300 3l. 2 030 38,000 22. 2 040 37, 000 18. 0

when `sand cast forming dies, permanent mold east tooling plate andpressure die cast shapes. are subjected to maximum stresses.

F-IG. 7 vshows the effect ofleadon tensile strength in a zinc base alloycontaining .4% aluminum, 3.25 copper,

.01% magnesium, V.01% beryllium, balance zinc, as cast inthe fsolidline, and -the broken ,line shows theteffeet of lead on thewtensilestrength of the samealloy rwhen cast and after agingLfor 1 year.A It`will be notedthat in the' as cast line, the ytensile strength of thealloy drops voli considerably after .004% lead and also drops olf intheline denoted for the aged alloy.

FIG. 8 is a char-t -showing the etfectof lead on `impact strength of analloy containing 4% aluminum, 3.25%

copper, .01% magnesium. and .01% bery11ium, balance zinc as cast byLthesolid line..-and after agnsfor 1 year:

in the broken line. Also in this -chart itis noted that both lines dropotlgafterg.()04% lead.

Therefore, it is to be noted that when the `lead content otanalloyis'rnore than .004470, such .percentage is detrimentalto the alloy,and-that, therefore, the'lead content ofY the alloy must be keptbelow/004% Table 6 :given below `Gontalis vrthe test data used vto iplot the graph of FIG. 7.

Table 6 Elect of lead on vthe tensile strength-and `impact strength of asand cast zinc base alloy containing 4% aluminum, 3.25% Copper, .01magnesium, .01% beryllium, balance zinc as cast.

Tensile Impact Percent Pb strength strength (psi.) (tt. lbs.)

Table 7 given below contains the test data used to plot the graph ofFIG. 8;

Table 7 Effect of lead on the tensile strength and `impact strength of asand lcast zinc base alloy containing y4% aluminum, 3.25 copper, .01%magnesium, .01%beryllium, balance Zinc when aged 1 year, at roomtemperature.

AGED

Tensile ,Impact Percent Pb strength strength (psi.) (tt. lbs.)

Asexplained above, other contaminants into the alloy such astin',,cadmium,fbis1nuth, and an.

.timony which, together with lead, fform the soft metal contaminants. Asexplained above, ,leadisthe -most important contaminant anclmust not beover 004%.

may enter Tin vmust have -a maximum. of- 001%,Vv cadmium must havelamaximum of ,001%, bismuth must have a maximum of .0005% and antimonymusthave a maximum of .0001%. Thus the `soit metal contaminants must nothave a collective maximum of more than 00,66%.

Iron can have a maximum of A.02% and silicon can have a maximum `of003%. Other metals which include manganese,chromiumand titanium, cannothave arnaximnm of over .005%. Therefore all of the contaminants inthealloy mustnot be over '.0346%.

Thus it can jbe seen that the alloy of the present invention issubstantially pure and in fact is very close to pure.

FIGS. 9 and '10, present,:in;bar graph form, the ycomparativey sand casttensilestrengthiand comparative sand cast impact. strength ,obtained'fromxfour alloys designated A, B. C, and 1). Alloy A'is the equivalentof the A.S.T.M. Alloy XXI comprising 4% aluminum, 3% copper, .05%magnesium and balance'zinc of'high purity; Alloy B` is La preferred.composition of PatentV No. 2,940,846 and contains 4% aluminum; 3.25%copper,

.005% magnesium and Ibalance zinc of high purity; Alloy C isia preferredcomposition of Patent No. 3,037,859 and contains 3% aluminum, 8% copper,.05% magnesium, .05% .beryllium andfbalance zinc of yhigh purity, and

Alloy D 'is;the alloy of this invention having about the Alloy Tensilestrength Impact strength (psi.) (it. lbs.)

An additional evaluation of lthe alloy of this invention is obtained byconsulting FIGS. 1l, 12,13 and 14. These iigures are photo micrographsof alloys designated A, B; C, and D respectively.

It will be seen that the alloy of this invention-repre sentis anextension of the art with this class of alloy. The addition ofV a small,but highly critical amount of beryllium in the`V range of .005% to .012%to an. alloy of zinc base containing 4% aluminum, .01% magnesium andcopper in the range from about .5% to about 3.5%, impartsv a remarkableimprovementin vthe tensile ystrength and a lsubstantialimprovement in:the impact strength', this is particularly thevca-se with the preferredalloy of this invention containing abouty 4% aluminum, about 3.25%copper and about .01% magnesium.

i An example; of a specific manufacturing procedure for producing thealloy'of myrinvention is given below.

High purity copperin the form of wire or ingot` is added tothe correctamount of molten high purity `zinc at 900 F.A When all, ofther copper isin solution, the correct aamount of vhigh purity `aluminum V,is vaddedto the molten1 alloy'. After solution and agitation, the molten alloy isskimmed. After skimming, Aa sufficient amountofcopper-aluminum-beryllium Master .Alloy is added in order to introduceberyllium into the alloy. The LMaster Alloyv is prepared byl melting Tasuiiicient amount-of pure aluminum in a graphite l,Crucible Vat about1300 F.V after which a predetermined amount of 96%` copper- 4%.beryllium alloy vis added. A Master Alloy of the following compositionis obtained: Copper 57.8%, aluminum 39.75%, berylliumV 2.41% agitationat.900 F. readily introducesy this master alloy into the melt. Finally,the Vstick magnesium ot high purity is then addedin sufcient amount ltointroduce .01%.

Intermittent slow Before adding the beryllium master alloy and themagnesium, it may be desirable to deoxidize the zincalurninum-coppermelt. This is done while maintaining the temperature at approximately900 F. by adding about .0005% of pure elemental lithium metal. Afterthis addition of lithium, the resulting mixture is strongly agitatedmechanically for about 45 minutes. Very thorough hand skimming of alldross and other nonmetallic residues concludes this deoxidation,desulphurization and oxide reduction operation. When excessive oxide,sulphur, or both are suspected in the metal, amounts of lithium greaterthan .0005% may be added. This excess lithium is removed preferentiallyby gassing the molten metal with nitrogen at from about 900 to about 950F. The reaction is symbolized Iby the following chemical equation:

The desirability of removing excess lithium is based upon the adverseeffect of lithium upon impact strength and an undesirable colorationimparted to sand cast shapes after aging.

It is to be understood that the foregoing description has been givenonly by way of illustration and example, and that changes andmodifications in the present disclosure, which will be apparent to aperson skilled in the art, 4are contemplated as being Within the scopeof the present invention, which is limited. only by the claims whichfollow.

I claim:

1. A zinc base alloy of high purity consisting essentially of, byweight, aluminum 3.8% to 4.2%, copper 1.5% to 3.25%, magnesium .005% to.025%, beryllium .005% to .012%, and having as impurities soft metalcontaminants 'not greater in collective amount than .0066%, iron notmore than .02%, the balance zinc.

2. A zinc base alloy of high purity consisting essentially of, byweight, aluminum 4%, copper 3.25%, magnesium .01%, beryllium .01% withsoft metal contaminants not 10 greater in collective amount than .0066%,iron not more than .02%, and the balance zinc.

3. A zinc base alloy of high purity consisting essentially of, byweight, about 3.5% to about 4.5% aluminum, labout .5% to about 3.5%copper, about .005% to about .025% magnesium, from about .0002% to about.02% beryllium, and impurities consisting of soft metal contaminants andiron, the soft metal contaminants being not greater in collective amountthan .0066%, iron being not greater than .02% and the balance zinc.

4. A zinc base alloy of high purity consisting essentially of, byWeight, about 3.5% to about 4.5% aluminum, about .5% to about 3.5copper, about .005% to about .025% magnesium, about .0002% to about .02%beryllium, and impurities consisting of soft metal contaminants andiron, the soft metal contaminants being tin not more than .001%, cadmiumnot more than .001%, lead not more than .004%, antimony not more than.0001% and bismuth not more than .0005 and iron not more than .02% andthe balance zinc.

References Cited by the Examiner UNITED STATES PATENTS 2,385,497 9/ 1945Bunn 75--178 2,467,956 4/ 1949 Bierman 75-178.2 2,631,936 3/1953Kuhlmann 75--135 2,837,427 6/1958 Monaco 75-178 3,037,859 6/1962 Larrieu75-178.2 3,083,096 3/1963 Larrieu 75--178.2 3,094,412 6/ 1963 Kaess etal. 75-135 FOREIGN PATENTS 1,110,429 7/ 1961 Germany.

638,733 6/ 1950 Great Britain.

111,444 2/ 1962 Pakistan.

DAVID L. RECK, Primary Examiner.

WINSTON A. DOUGLAS, Examiner.

1. A ZINC BASE ALLOY OF HIGH PURITY CONSISTING ESSENTIALLY OF, BYWEIGHT, ALUMINUM 3.8% TO 4.2%, COPPER 1.5% TO 3.25%, MAGNESIUM .005% TO.025%, BERYLLIUM .005% TO .012%, AND HAVING A IMPURTIES SOFT METALCONTAINMENTS NOT GREATER IN COLLECTIVE AMOUNT THAN .0066%, IRON NOT MORETHAN .02%, THE BALANCE ZINC.